U.S. patent application number 12/522413 was filed with the patent office on 2010-05-27 for piston ring with a multilayer assembly, and a method for the production thereof.
Invention is credited to Michael Buchmann, Marc-Manuel Matz, Johann Riedl, Peter Schmidt.
Application Number | 20100127462 12/522413 |
Document ID | / |
Family ID | 39167856 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100127462 |
Kind Code |
A1 |
Buchmann; Michael ; et
al. |
May 27, 2010 |
PISTON RING WITH A MULTILAYER ASSEMBLY, AND A METHOD FOR THE
PRODUCTION THEREOF
Abstract
The present invention relates to a piston ring with improved
running-in and wear behaviour as well as to a method for the
production thereof. According to a first embodiment, the piston
ring comprises a ring body (2), an adhesive promoter layer (4) of a
Ni-alloy applied to the bearing surface of the ring body (2) by
thermal spraying, a wear-resistant coating (6) of a Mo-alloy with
CrC, WC, MoC applied to the adhesive promoter layer (4) by thermal
spraying; and a running-in layer (8) of an AlCu-alloy or
Ni-graphite-alloy applied to the wear-resistant coating (6) by
thermal spraying. According to a second embodiment, the piston ring
comprises a ring body, an adhesion layer applied to the bearing
surface of the ring body, and a running-in layer, comprising nickel
graphite, that is applied to the adhesion layer.
Inventors: |
Buchmann; Michael;
(Stuttgart, DE) ; Schmidt; Peter; (Neunkirchen
Seelscheid, DE) ; Matz; Marc-Manuel; (Friedberg,
DE) ; Riedl; Johann; (Friedberg, DE) |
Correspondence
Address: |
DICKINSON WRIGHT PLLC
38525 WOODWARD AVENUE, SUITE 2000
BLOOMFIELD HILLS
MI
48304-2970
US
|
Family ID: |
39167856 |
Appl. No.: |
12/522413 |
Filed: |
November 26, 2007 |
PCT Filed: |
November 26, 2007 |
PCT NO: |
PCT/EP07/10259 |
371 Date: |
July 8, 2009 |
Current U.S.
Class: |
277/444 ;
427/451 |
Current CPC
Class: |
C23C 4/02 20130101; F16J
9/26 20130101; C23C 4/06 20130101; C23C 4/067 20160101; C23C 4/08
20130101 |
Class at
Publication: |
277/444 ;
427/451 |
International
Class: |
F16J 9/26 20060101
F16J009/26; C23C 4/10 20060101 C23C004/10; F02F 5/00 20060101
F02F005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 9, 2007 |
DE |
10 2007 001 377.0 |
Claims
1. A piston ring, comprising: a ring body; an adhesive promoter
layer of a Ni-alloy applied to the bearing surface of the ring body
by thermal spraying; a wear-resistant coating of a Mo-alloy with
CrC, WC, MoC applied to the adhesive promoter layer by thermal
spraying; and a running-in layer of an AlCu-alloy or Ni
graphite-alloy applied to the wear-resistant coating by thermal
spraying.
2. Piston ring according to claim 1, wherein the adhesive promoter
layer, the wear-resistant coating and the running-in layer are
applied in oversprayed form.
3. Piston ring according to claim 1, wherein the flank of the ring
body has a bevel at their edges.
4. Piston ring according to claim 1, wherein the ring body has gas
discharge slots having a bevel at its edges.
5. Piston ring according to claim 3, wherein the bevel has an angle
of 30.degree. to 70.degree..
6. Piston ring according to claim 5, wherein the bevel has a width
of 0.5 to 2.0 mm.
7. Method for the production of a piston ring, comprising:
providing a ring body; thermal spraying of an adhesive promoter
layer of a Ni-alloy on the bearing surface of the ring body;
thermal spraying of a wear-resistant coating of Mo-alloy with CrC,
WC, MoC on the adhesive promoter layer; and thermal spraying of a
running-in layer of an AlCu-alloy or Ni graphite-alloy on the
wear-resistant coating.
8. Method according to claim 7, wherein the adhesive promoter
layer, the wear-resistant coating and the running-in layer are
applied in oversprayed form.
9. Method according to claim 7, wherein the thermal spraying is
selected from a group consisting of at least one of: an arc wire
coating method; a wire flame coating method; atmospheric plasma
spraying, APS; and high velocity oxy-fuel flame spraying, HVOF.
10. Method according to claim 7, further comprising: providing the
flank of the ring body with a bevel at its edges, prior to spraying
of the adhesive promoter layer.
11. Method according to claim 7 one, wherein the ring body has gas
discharge slots, further comprising: providing the gas discharge
slots with a bevel at their edges, prior to spraying of the
adhesive promoter layer.
12. Method according to claim 10, wherein the bevel has an angle of
30.degree. to 70.degree..
13. Method according to claim 12, wherein the bevel has a width of
0.5 to 2.0 mm.
14. Piston ring, comprising a ring body, a wear-resistant coating
applied to the bearing surface of the ring body and a running-in
layer applied to the wear-resistant coating, and wherein the
running-in layer comprises nickel graphite.
15. Piston ring according to claim 14, wherein the wear-resistant
coating comprises hard chrome, chrome with aluminium oxide ceramics
or chrome with micro diamond.
16. Piston ring according to claim 14, wherein the running-in layer
has a layer thickness of 20 to 400 .mu.m.
17. Piston ring according to claim 16, wherein the running-in layer
has a graphite content of 10 to 40 Vol.-%.
18. Method for the production of a piston ring, comprising the
steps: providing a ring body; applying a wear-resistant coating to
the bearing surface of the ring body; activating the wear-resistant
coating; and applying a running-in layer to the wear-resistant
coating; and wherein the running-in layer comprises nickel
graphite.
19. Method according to claim 18, wherein the applying of the
wear-resistant coating is performed by a thermal spraying
method.
20. Method according to claim 19, wherein the applying of the
wear-resistant coating is performed by atmospheric plasma spraying
or high velocity oxy-fuel flame spraying.
21. Method according to claim 18, wherein the wear-resistant
coating comprises hard chrome, chrome with aluminium oxide ceramics
or chrome with micro diamond.
22. Method according to claim 18, wherein the wear-resistant
coating is activated by a blasting process or thermally.
23. Method according to claim 18, wherein the applying of the
running-in layer is performed by a thermal coating method.
24. Method according to claim 18, wherein the applying of the
running-in layer is performed by plasma spraying or powder flame
spraying.
25. Method according to claim 18, wherein the running-in layer has
a layer thickness of 20 to 400 .mu.m.
26. Method according to claim 18, wherein the running-in layer has
a graphite content of 10 to 40 Vol.-%.
27. The piston ring according to claim 4, wherein the bevel has an
angle of 30.degree. to 70.degree..
28. The piston ring according to claim 27, wherein the bevel has a
width of 0.5 to 2.0 mm.
29. The method according to claim 11, wherein the bevel has an
angle of 30.degree. to 70.degree..
30. The method according to claim 11, wherein the bevel has a width
of 0.5 to 2.0 mm.
Description
[0001] The present invention relates to a piston ring and a method
for the production thereof, particularly a large-bore piston ring
with a multilayer coating for an internal combustion engine.
[0002] With piston rings as for example those of internal
combustion piston engines there are two demands to be fulfilled
which are per se conflicting. On the one hand, a high
wear-resistance has to be present, because otherwise, i.e. with
thinning piston ring, the gas leakage and the oil consumption could
increase as well as the performance of the engine could decrease.
By a wearing off piston ring the gap between cylinder wall and
piston ring becomes bigger and bigger, so that combustion gases can
easier escape past the ring (so-called blow-by) which reduces the
efficiency of the engine. By an enlarged gap furthermore the not
stripped oil film remaining in the combustion space becomes
thicker, so that more oil per time unit can get lost, thus the oil
consumption is increased.
[0003] To achieve as optimal as possible engine properties, thus to
achieve the best possible compromise between maximum seal effect
and low friction losses, hence the dimension of the gap between
piston ring(s) and cylinder wall must be maintained as exactly as
possible. However, this would require complex and expensive process
steps in the production and assembly of the engine, because
otherwise it always comes to a certain degree of inevitable
tolerance. Normally, a perhaps slightly too small gap dimension is
accepted, the piston ring being further allowed to achieve the
optimum thickness by friction wear during operation. Ideally, the
bearing surface of the piston ring wears off until the optimal gap
diameter is achieved. This process is also called running-in.
[0004] On the one hand, a material as wear-resistant as possible is
desired to achieve that the piston ring wears out as little as
possible in the regular operation and the gap hardly increases. To
achieve good running-in properties, however, at least a part of the
bearing surface must be able to be rubbed off comparatively easily,
so that a, perhaps (e.g., due to inevitable component tolerances)
too small gap between piston ring and cylinder wall can extend as
quickly as possible to the right dimension during the running-in
operation.
[0005] Hence, in principle piston rings are provided with coatings
which should produce the desired qualities. This is naturally
easier to handle and cheaper as to produce the complete piston ring
from a possibly expensive material with the desired properties.
With such coatings another requirement comes along. In additional
to providing the necessary qualities, the coating has also to have
such composition that it does not separate from the piston ring,
i.e. such that it exhibits good adhesion with the underlying
material. Provided that the coating consists of several different
layers, further a good coherence between the layers is necessary,
that is, a good cohesion. Otherwise there is the danger of the
formation of cracks or separation of the layers which can be
dangerous for the engine.
[0006] Coatings on the bearing surfaces of piston rings have to be
wear-resistant in the surface area being in contact with the
cylinder wall. In addition, its own wear in the running-in phase
should be sufficient for an adequate adjustment to the counter
surface. Moreover, these layers should be highly resistant to
breakouts and also exhibit no or only very slight fatigue even
after long periods of use.
[0007] Wear-resistant coatings are produced, for example, of hard
chrome. DE 199 31 829 A1 describes a galvanic hard chrome layer for
a piston ring. Other materials for wear-resistant coatings are
chrome with aluminium oxide ceramics (e.g., CKS.RTM. of the company
Federal Mogul) or chrome with micro diamond (e.g., GDC.RTM. of the
company Federal Mogul).
[0008] Running-in layers applied to CKS.RTM.-wear-resistant
coatings are based, for example, on molybdenum applied by means of
wire flame spraying on the wear-resistant coating. Here the
wear-resistant coating is activated by a blasting process prior
thereto.
[0009] Furthermore, a running-in layer of an AlCuFe-alloy can be
applied to a CKS.RTM.-wear-resistant coating by thermal spraying.
However, a galvanic intermediate layer has to be applied to the
CKS.RTM.-wear-resistant coating first.
[0010] However, the running-in and wear properties of common piston
rings with a wear-resistant coating based on chrome and a
running-in layer applied on top thereof still require an
improvement.
[0011] The task of the present invention is to provide a piston
ring with improved running-in and wear behavior as well as a method
for the production thereof.
[0012] According to a first embodiment of the invention a piston
ring is provided, comprising: [0013] a ring body; [0014] an
adhesive promoter layer of a Ni-alloy applied to the bearing
surface of the ring body by thermal spraying; [0015] a
wear-resistant coating of a Mo-alloy with CrC, WC, MoC applied to
the adhesive promoter layer by thermal spraying; and [0016] a
running-in layer of an AlCu-alloy or Ni-graphite-alloy applied to
the wear-resistant coating by thermal spraying.
[0017] The piston ring according to the invention, by the use of
three different functional layers, provides a new and advantageous
combination of wear-resistance (by the wear-resistant coating),
favorable running-in properties (by the running-in layer) as well
as an increased adhesion/cohesion (by the adhesion layer). It is
not necessary to rework or finish running-in layer, but it gets its
final form by the friction wear occurring in the running-in phase.
The wear-resistant coating prevents excessive wear under extreme
operating conditions of the engine. The adhesive promoter layer
provides for an optimum attachment of the layers on the bearer or
ring body.
[0018] Preferably the adhesive promoter layer, the wear-resistant
coating and the running-in layer are applied in oversprayed
form.
[0019] Preferably the ring body comprises gas discharge slots
having a bevel at its edges.
[0020] Preferably the bevel has an angle of 30.degree. to
70.degree.. Preferably the bevel has a width of 0.5 to 2.0 mm.
[0021] According to another aspect of the invention a method of the
production of a piston ring is provided according to the first
embodiment of the invention, comprising: [0022] providing a ring
body; [0023] thermal spraying of an adhesive promoter layer of a
Ni-alloy on the bearing surface of the ring body; [0024] thermal
spraying of a wear-resistant coating of a Mo-alloy with CrC, WC,
MoC on the adhesive promoter layer; and [0025] thermal spraying of
a running-in layer of an AlCu-alloy or Ni graphite-alloy on the
wear-resistant coating.
[0026] The adhesive promoter layer, the wear-resistant coating and
the running-in layer are preferably applied in oversprayed
form.
[0027] Preferably, the thermal spraying includes the following
coating methods: [0028] an arc wire coating method; [0029] a flame
coating method; [0030] atmospheric plasma spraying, APS; and [0031]
high velocity oxy-fuel spraying, HVOF.
[0032] Preferably, the method comprises further: [0033] providing
to the flank of the ring body with a bevel at its edges, prior to
spraying of the adhesive promoter layer.
[0034] If the ring body has gas discharge slots, the method
preferably comprises further: [0035] providing the gas discharge
slots with a bevel at its edges, prior to spraying of the adhesive
promoter layer.
[0036] Preferably, the bevel has an angle of 30.degree. to
70.degree.. Further preferably, the bevel has a width of 0.5 to 2.0
mm.
[0037] FIG. 1 shows the step of the edge trimming or beveling of
the piston ring;
[0038] FIG. 2 schematically shows angle and width of the bevel;
[0039] FIG. 3 shows the step of spraying of the adhesive promoter
layer; and
[0040] FIG. 4 shows the completely coated piston ring according to
the invention.
[0041] Coatings on the bearing surfaces of piston rings need, in
addition to a good and temperature-resistant attachment (adhesion)
to the carrier and a good and temperature-resistant bonding within
the layer (cohesion), also to be wear-resistant in the surface area
being in contact with the cylinder wall. Beyond that, its own or
inherent wear in the running-in phase should be sufficient for an
adequate adjustment to the counter surface. Beyond that, these
layers should be highly resistant to breakouts and also exhibit no
or only very slight fatigue even after long periods of use.
[0042] Hence, the underlying object of the present invention is to
provide the bearing surfaces of piston rings with wear-resistant
layers applied by a flame spraying method, which can withstand the
extreme loads, but at the same time show a good running-in
behavior. The method of the production of the layers should be as
simple as possible and cost-saving, and above all it should enable
to produce the wear-resistant coatings with properties adjusted to
the respective use case.
[0043] According to the invention this job is solved in the first
embodiment by a coating which consists of at least three superposed
different sprayed layers: an adhesive promoter layer, a
wear-resistant coating on top thereof, and an exterior running-in
layer. Adhesion and cohesion can be further improved by suitable
beveling of edges at ring flank and gas discharge slots prior to
the coating.
[0044] In FIG. 1 is shown in a cross section view how the piston
ring is beveled. On the bearing surface side (on the left in the
figure) the edges of the piston ring 2 can according to the
invention be provided with a bevel 10 prior to the coating. The
angle .alpha. of the bevel 10 can according to the invention be
from 30.degree. and 70.degree., wherein in FIG. 2 a corner of
45.degree. is shown as example. Furthermore, according to different
embodiments of the invention the bevel 10 can have a width d of 0.5
up to 2 mm. The beveling of edges is an optional step in the
production of the piston ring and the bevel is an optional
characteristic of the finished piston ring according to the
invention, respectively. The beveling can be carried out with every
suitable known method.
[0045] FIG. 3 shows in a cross section view the step of the
application of the first layer of the coating. An adhesive promoter
layer 4 is applied on the ring body 2. According to the invention
this is accomplished by means of a thermal spraying method,
including high velocity flame spraying (high velocity oxy-fuel
spraying, HVOF), atmospheric plasma spraying (APS), arc wire or
wire flame coating method. This is illustrated by a HVOF
arrangement 12 as an example. The adhesive promoter layer 4 is a
nickel-alloy.
[0046] In further steps (not shown in the figures) a wear-resistant
coating as well as a running-in layer are applied above the
adhesive promoter layer. This can be performed in the same manner
as the application of the adhesive promoter layer by one of the
above mentioned thermal spraying methods, wherein also different
methods can be used for respective different layers. The layer
design is FF; that means oversprayed.
[0047] According to the first embodiment the wear-resistant coating
of the invention is a molybdenum-alloy with chrome carbide CrC,
wolfram carbide WC or molybdenum carbide MoC.
[0048] The running-in layer applied at last is not reworked on its
surface, but rather obtains its final form during the running-in
phase of the engine through friction wear.
[0049] In FIG. 4 the finished piston ring according to the first
embodiment of the invention is shown in a cross section view,
comprising the ring body 2, the adhesive promoter layer 4, the
wear-resistant coating 6 and the running-in layer 8.
[0050] According to a second embodiment of the present invention a
piston ring comprises a ring body, a wear-resistant coating applied
on the bearing surface of the ring body, and a running-in layer
applied on the wear-resistant coating. The running-in layer
comprises nickel-graphite (Ni--C-alloy). The piston ring is
preferably a large-bore piston ring for an internal combustion
engine.
[0051] The piston ring according to the second embodiment of the
invention by the use of the two different functional layers
provides a new and advantageous combination of wear-resistance (by
the wear-resistant coating) and favorable running-in qualities (by
the running-in layer of nickel graphite). It is not required to
rework or finish the running-in layer, but it obtains its final
form through the friction wear occurring in the running-in phase.
The wear-resistant coating prevents excessive wear under extreme
operating conditions of the engine.
[0052] Preferably, the wear-resistant coating comprises hard
chrome, chrome with aluminum oxide ceramics (e.g., CKS.RTM. of the
company Federal Mogul) or chrome with micro diamond (e.g., GDC.RTM.
of the company Federal Mogul).
[0053] Preferably the running-in layer has a layer thickness of 20
to 400 .mu.m. Furthermore, preferably the running-in layer has a
graphite content of 10 to 40 Vol.-%.
[0054] According to a further aspect of the invention a method of
the production of a piston ring according to the second embodiment
of the invention is provided. It comprises the steps: [0055]
providing a ring body; [0056] applying a wear-resistant coating on
the bearing surface of the ring body; [0057] activating the
wear-resistant coating; and [0058] applying a running-in layer on
the wear-resistant coating.
[0059] Here the running-in layer comprises nickel graphite.
[0060] Preferably, the applying of the wear-resistant coating is
performed by a thermal spraying method. Preferably, the thermal
spraying method is atmospheric plasma spraying (APS, e.g., MKP) or
high velocity oxy-fuel flame spraying (HVOF, e.g., MKJet.RTM. of
the company Federal Mogul).
[0061] Preferably, the wear-resistant coating comprises hard
chrome, chrome with aluminum oxide ceramics (e.g., CKS.RTM. of the
company Federal Mogul) or chrome with micro diamond (e.g., GDC.RTM.
of the company Federal Mogul).
[0062] The wear-resistant coating is preferably activated by a
blasting process or thermally.
[0063] The applying of the running-in layer is preferably performed
by a thermal coating method. Preferably, the thermal coating method
is atmospheric plasma spraying (APS, e.g., MKP) or high velocity
oxy-fuel flame spraying (HVOF, e.g., MKJet.RTM. of the company
Federal Mogul).
[0064] Preferably, the running-in layer has a layer thickness of 20
to 400 .mu.m. Furthermore, preferably the running-in layer has a
graphite content of 10 to 40 Vol.-%.
* * * * *